The present invention relates to oxygen sensing and more particularly concerns a small, portable self-contained instrument for secondary oxygen sensing.
In inhalation therapy a patient is provided with a controlled oxygen breathing mixture that is generally oxygen enriched air and often humidified or moisturized. The controlled oxygen breathing mixture is either provided for the interior of an enclosure or tent that surrounds the patient or is provided by inhalation therapy tubing connected between an oxygen percentage controlling device, such as for example a nebulizer or humidifier, and a breathing mask of the patient. The breathing mixture is provided for the patient by mixing ambient air with pure oxygen gas. The mixture is established and controlled by various types of oxygen control apparatus. Such apparatus may include gauges for precision reading and control of oxygen percentage and mixture flow rates and pressures or may comprise a nebulizer with built-in adjustable controls for establishing and maintaining percentage of oxygen in breathing mixtures provided to the patient.
Although breathing oxygen percentage and other components of breathing mixtures are established and maintained by primary mechanisms at the breathing mixture source, it is useful and even necessary from time to time to monitor the oxygen content of a breathing mixture actually transmitted to the patient. Thus, it is desirable for an attendant to be able to readily and conveniently monitor oxygen content at or close to the patient without adjusting or controlling remote primary oxygen sources.
Systems and apparatus presently available for gas monitoring include relatively large complex electrical devices and mechanisms, most of which are not readily portable. Some systems include a box containing monitoring and electronic circuitry connected by a long cable to a standard type of oxygen sensor. Typical of such oxygen sensors are those described in U.S. Pat. No. 4,367,133 and U.S. Pat. No. 4,077,861. The sensor generates an electrical current signal indicative of percentage of oxygen, or actually indicative of partial pressures of oxygen, and such electrical signal is transmitted to standard types of electronic circuitry for indication of oxygen content of gas being monitored. The monitoring equipment thus includes several different parts, a box or container, a sensor holder, sensor electric coupling and interconnecting cabling. Equipment of this type is relatively inconvenient to handle, store and carry. Therefore it is not readily carried about by an attendant who moves from one patient to another for various service tasks only one of which may comprise monitoring of oxygen concentration of breathing mixtures.
Accordingly, it is an object of the present invention to provide a portable oxygen sensor that avoids or minimizes above mentioned problems.